Spark compressor and trigger for spark discharge light



Jan. 19, 1960 N. B. STEVENS ETAL 2,922,066

SPARK COMPRESSQR AND TRIGGER FOR SPARK DISCHARGE LIGHT Filed NOV. 13, 1956 Fig I SUPPLY x 50 74; \x

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2,922,066 Patented Jan. 19, 1960 SPARK COMPRESSOR AND TRIGGER FOP. SPARK DISCHARGE LIGHT Norman B. Stevens, Corona, and John A. Hart, Riverside,

Calif., assignors to Motorola, Inc., Chicago, 111., a corporation of Illinois Application November 13, 1955, Serial No. 621,601

Claims. (Cl. 313-205) This invention relates to new and useful improvements in electric spark discharge lights, and more particularly to an improved spark discharge light in which one of the spark electrodes is recessed within a trigger electrode.

In recent years there have been developed improved electric spark discharge lights for producing high brightness and/or intensity light flashes of short duration. These spark discharge lights have proved to be very efiective as high intensity light sources for photographic work, for stroboscopic observation, and for optical range finding equipment. In the electric spark discharge light, a high voltage DC. power supply is used to charge an electrical condenser which is then discharged across a pair of spark electrodes. In some spark discharge lights, a trigger electrode is used to provide an ionized path for the initiation of the discharge of a spark be tween the main spark electrodes. In the development of spark discharge lights, one problem which has arisen and which has not been satisfactorily solved is that of the wandering of the electric spark. This wandering frequently causes the useably bright part of the discharge to occur outside the useful region.

It is therefore one object of this invention to provide an improved spark discharge light which is capable of producing a high brightness confined spark.

Another object of this invention is to provide an improved spark discharge light in which the spark discharge is compressed to provide a light flash of substantially higher brightness.

A feature of this invention is the provision of an electric spark discharge having a pair of spark discharge electrodes and a trigger electrode, with one of the spark discharge electrodes being recessed within the trigger electrode.

Another feature of this invention is the provision of a spark discharge light having a pair of spark discharge electrodes and a trigger electrode having an aperture extending therethrough with one of the spark discharge electrodes being recessed in said aperture and insulated from the trigger electrode.

Other objects and features of this invention will become apparent from time to time throughout the specification and claims as hereinafter related.

In the accompanying drawings, to be taken as a part of this specification, there is clearly and fully illustrated a preferred embodiment of this invention, in which drawings:

Fig. l is a view in cross-section of an improved spark discharge light and showing a schematic wiring diagram for the light, and

Fig. 2 is a plan view of the trigger electrode and recessed spark electrode of the spark discharge lamp shown in Fig. 1.

This invention comprises an improved spark discharge light having a pair of spark discharge electrodes and a trigger electrode. In this spark discharge light the trigger electrode is of cylindrical or cup-shaped construction, having a central aperture aligned with an aper- 2. ture in insulating material adjacent thereto and having one of the spark discharge electrodes mounted concentrically with and spaced from the trigger electrode so that the spark discharge is compressed into the passage formed by the aperture in the insulating material and by the aperture in the trigger electrode. This structural restriction of a portion of the spark discharge path is operable to reduce wander of the spark and to confine the spark to produce a substantially greater intensityof light generated by the spark. The brightness of the spark in the aperture of the trigger electrode exceeds.

conventional spark discharge lights by to percent. Referring to the drawings by numerals of reference and more particularly to Fig. 1 there is shown a sparkdischarge light assembly 10 which is mounted on a base 12 (which may be one end of the casing of a capacitor 74) which is grounded as at 13. The base 12 has supporting and conducting members 14. and 16 mounted thereon which support at their other end a cup-shaped supporting and conducting member 18 which is held in position by a plurality of bolts or screws 20. The supporting member 18 supports a spark discharge electrode 22 which extends into a trigger electrode assembly 24. The trigger electrode assembly 24 is supported on the supporting member 18 and insulated therefrom by an insulating member 26. 4

The trigger electrode assembly 24 consists of a cupshaped metal base member 28 which may be of brassor copper and a disk-shaped trigger electrode 30 which is preferably of molybdenum and secured in place by a ing member 28 and the molybdenum trigger 30. The

trigger assembly 24 has an aperture 32 extending through the trigger 30 and the insulating member 34 which receives the spark electrode 22. As shown in Fig. l, the spark electrode is positioned with its blunt discharge end recessed in the insulating member so that it forms an inner end surface of the insulator aperture. fined passage or channel thus formed is aligned with the trigger aperture and has a depth dimension on the order of the cross sectional diameter of the insulator aperture. The trigger electrode 30 is provided with an electrical connector 36 which extends into a recess in the supporting member 28 and which extends through an aperture 40 in the supporting member 18. The electrical connector 36 is supported on an insulator member 38 in the aperture 40. At the base portion of the spark light assembly there is positioned a threaded electrical connector 42 for a second spark discharge electrode 44. The spark electrodes 22 and 44 may be made of tungsten. The spark discharge electrode 44 is supported by a metal cylinder 46 which provides for adjustment of the electrode 44 by means of the set-screw 91. The connector 42 is insulated from the base member 12 by a supporting insulator 45. When the spark discharge light is energized a spark discharge 48 will occur between the electrodes 22 and 44 in a manner which will be subsequently described.

The spark discharge light assembly 10 is provided with:

a high voltage DC. power supply 50 which may produce a voltage of the order of 5,000 to 10,000 volts. The high voltage power supply 50 is connected through a lead 51 to one side of a resistor 52, the other side of which is connected by a lead 53 to the connector 42 which provides an electrical connection to the spark discharge electrode 44. The resistor 52 preferably has a high resistance of the order of 500,000 ohms. The other side of the high voltage power supply 50 is connected by electric leads 56 and 58 to ground as indicated at 60.

The con-' The electrical lead 56 is also connected at 62 to I one end of the primary coil 64 of a spark coil assembly 66. The other end of the primary coil 64 is connected to a resistor 68 which is in turn connected to a DC. power supply 70 which is grounded as at 72. The resistor 68 has a resistance of the order'of 47,000 ohms and the DC. power supply is of the order of 150 volts. There is also provided a capacitor 74 which may have a capacitance of the order of 0.5 mid. and rated at 5,000 volts, connected between the lead53 at the end of the resistor 52 and the ground connection point 62 at one end of the primary coil 64. A switch means 76 is connected from a point between the primary coil 64 and resistor 68 to the lead 58. The switch means 76 is shown as a simple switch but in most assemblies would preferably be a switch tube circuit arrangement of known design. There is-also provided a capacitor 78, having a capacitance of the order of 0.1 mid. and rated at 200 volts, connected in parallel with the switch means 76 from a point between the coil 64and resistor 68 to a point on the lead 58.

The spark coil 66 has a secondary coil 8!} which is connected to the point 62 which provides a ground connection. The other end of the secondary coil 80 is connected by the lead 86 to one side of the capacitor 88 the other side of which is connected by a lead 90 to the connector 36 for the trigger electrode assembly 24. The. capacitor 88 preferably has a capacitance of the order of 0.001 mid. and rated at 5,000 volts.

' Operation a The circuit which has been described for this electric discharge spark light assembly is a standard circuit for spark discharge lights and functions in a standard manner. The capacitor 74 is charged from the high voltage power supply 50. The capacitor 78 is charged from the low voltage power supply 70. 76 is closedthe capacitor 78 is discharged and a current pulse-passes through the primary coil 64 of the spark coil assembly 66. The pulse of current through the primary I 64 causes a high voltage electric pulse to be induced in the secondary coil 80' and passed through the leads 86 and 90 and capacitor 88 to the connector 36 for the trigger electrode 24. The circuit for the electric pulse from the secondary coil 80 is-completed through the ground connection point 62 which is in common with ground 13 for the spark electrode'22. The electric pulse from the secondary coil 80 causes a spark to jump between the trigger-electrode 30 and the spark electrode 22.

The spark discharge from the trigger electrode causes an ionized path to be produced which permits the discharge of a high intensity spark between the spark electrodes 22 and 44. NVhen the trigger electrode fires its spark the capacitor 74 discharges through the spark electrodes 22 and 44 to produce a high intensity spark therebetween. Because of'the fact that the electrode 22 is recessed in the aperture or passage 32 in the insulator 34 the tendency of the electric spark 48 to expand is restricted, and the spark in effect is compressed and a spark light of'substantially higher brightness is formed. The brightness of a spark discharge light has been found to be greater immediately adjacent to the trigger electrode. Since the spark discharge in this assembly occurs between the electrode 44 and the electrode 22 which is recessed Within the trigger electrode 24 and insulator 34, the entire spark must pass through the hole in trigger When the switch means power supplies, resistors and capacitors. It is to be understood that these specific values were intended to illustrate a particular operating example of this invention. It is obvious that any electrical engineer skilled in this art could select or design an electric circuit using other voltages, resistances, and capacitances than those specifically mentioned herein. This spark light assembly should therefore be considered to be applicable for use i With any suitable energizing circuit.

We claim: 1. A spark discharge device including'in combination, first and second spark electrodes having spaced ends and A adapted to be connected in a high voltage circuit for discharge of a high energy spark in a path between said ends, a trigger electrode having an aperture therethrough and positioned between the spaced ends of said spark electrodes with said aperture aligned with the spark path for passage of a spark discharge therethrough, insulating 7 means, surrounding one of'said spark electrodes and havtrigger a discharge between said spark electrodes.

2. A spark discharge device for producing high energy pulsed light, said device including in combination, first and second spark electrodes having spaced ends defining a spark discharge path therebetween, insulating means surrounding said first spark electrode and having an 1 elongated aperture therethrough, said first spark electrode electrode assembly 24 and a higher light brightness is thus obtained. In this spark light assembly the light which is generated in the'aperture 32 in the trigger electrode assembly 24, has an intensity which is 75 to 100 percent greater than the light generated by an ordinary being positioned in said aperture with its end terminating within said insulating means, said aperture having such dimensions to confine a high energy spark discharge: passing therethrough for increasing the brightness level thereof, a trigger electrode positioned adjacent said aperture, said spark electrodes being adapted to be connected in a high voltage discharge circuit, and said trigger electrode and said second spark electrode being adapted to be connected in a high voltage trigger circuit for initiating an ionizing spark to trigger a high energy spark discharge through said aperture and between said spark electrodes.

3. A spark discharge device including in combination, first and second spark electrodes having spaced ends, a trigger electrode having a disk shaped portion, a cylindrically shaped insulator adjacent said disk shaped portion, said disk shaped portion of said trigger electrode and said insulator having aligned apertures therethrough having substantially the same cross section area as the cross .section area of the said first and second electrodes, said apertures constituting a channel having such dimensions to confine the spark discharge therethrough for increasing the brightness thereof, said first electrode being positioned in said insulator with its end terminating within said insulator aperture, said spark electrodes being adapted to be connected in a high voltage capacitive discharge circuit, and said trigger electrode and'said second spark electrode being adapted to be connected in high voltage capacitive discharge circuit to initiate an ionizing spark to trigger a discharge through said channel between said spark electrodes.

4. A spark discharge device as defined in claim 3 in which said first and second spark electrodes are formed of tungsten and said first electrode is positioned with its end terminating within said insulator so that the depth of the insulator aperture is on the order of the cross sectional diameter of said insulator aperture.-

5. A spark'discharge device for producing high energy pulsed light, said device including in combination, first and second spark electrodes having spaced ends defining a spark discharge path therebetween, insulated means:

having an elongated aperture therethrough, said means being positioned adjoining the discharge end of said first spark electrode with said discharge end forming one end of said aperture of said insulating means, said aperture having such dimensions to confine a high energy spark discharge passing therethrough for increasing the brightness level thereof, a trigger electrode positioned adjacent the other end of said aperture, said spark electrodes being adapted to be connected in a high voltage discharge circuit, and said trigger electrode and said second spark electrode being adapted to be connected in a high voltage trigger circuit for initiating an ionizing spark to trigger a high energy spark discharge through said aperture and between said spark electrodes.

References Cited in the file of this patent UNITED STATES PATENTS Soundry Mar. 12, Clifiord Sept. 9, Mayer June 7, Roberts May 11, McCarthy Feb. 26, Biondi July 16, Scott Aug. 20,

FOREIGN PATENTS Great Britain Oct. 19, Australia Aug. 21, 

